Cosmetics contain powders or pigments for improving coloration, feeling and the like. When powders or pigments are used for these purposes, it is required to uniformly disperse the powders or the pigments in cosmetics (cosmetic compositions) to obtain cosmetics having high dispersion stability without unevenness in color and the like. However, when ordinary powders or pigments are selected and dispersed in an aqueous dispersion medium, there is a need to hydrophilize (make a hydrophilic treatment) them for homogenizing property of the surface thereof. Without hydrophilization (hydrophilic-treatment), it is impossible to obtain cosmetics having good dispersibility and dispersion stability (dispersion stability with lapse of time).
Meanwhile, many proposals have been so far made for hydrophilicaly treating hydrophobic powders or pigments. Methods for mixing a hydrophilized (hydrophilicaly treated) silicone resin which is obtained by hydrophilizing (hydrophilicaly treating) a silicone resin having heat resistance, weather ability (weather resistance), electric insulating property, chemical resistance, water resistance, and the like as a powder in cosmetics have been studied (refer to Japanese Patent Kokai Publication JP-A-10-139624, Japanese Patent Kokai Publication JP-A-10-175816, Japanese Patent Kokai Publication JP-A-2002-235004 and Japanese Patent Kokai Publication JP-A-9-104833).
For example, it is proposed that the silicone resin is hydrophilicaly treated with surfactant such as nonionic surfactant, anionic surfactant, cationic surfactant, ampholytic surfactant or these mixture to disperse the silicone resin in an aqueous dispersion medium, and it is reported that a cosmetic (cosmetic of aqueous type) containing the dispersion which is obtained by dispersing the treated powder thus obtained into an aqueous dispersion medium can be improved in smooth feeling (refer to Japanese Patent Kokai Publication JP-A-10-139624, Japanese Patent Kokai Publication JP-A-10-175816 and Japanese Patent Kokai Publication JP-A-2002-235004).
However, since the silicone resin described above has an extremely strong water-repellent property (hydrophobic property), the method of hydrophilic treatment (surface treatment) with the above surfactant or a water-soluble polymer is said to be hard in being satisfactory for dispersing such powder (silicone resin) in an aqueous dispersion medium. When the hydrophilicaly treated (hydrophilicaly-treated) powder is incorporated into cosmetics therewith, the powder(s) or the pigment(s) is dissociated or separated in the system, and subsequently aggregates. Consequently, this causes uneven color or a difference between color in appearance (appearance color) and color at the time of application (application color) therein or dispersion stability with lapse of time is impaired, or in case of some form of cosmetics, the re-dispersibility of the powders or the pigments in the system may be worsened to cause caking and notably decreases its usability.
It is however quite difficult to disperse the above silicone resin (particles) in an aqueous dispersion medium by hitherto-proposed methods for hydrophilicaly treating hydrophobic powders or pigments.
For example, a hydrophilicaly surface treated pigment in which a hydrophilic organic group is introduced into a pigment using a hydrophilic silane compound or silane coupling agent and a composition containing the same are proposed (refer to Japanese Patent Kokai Publication JP-A-9-104833). However, the above-mentioned hydrophilicaly surface treated pigment (s) in which a hydrophilic organic group is introduced into a pigment using a hydrophilic silane compound or silane coupling agent aggregates in the system, and consequently an uneven color is caused or a conformity between color in appearance and color at the time of application worsens, so that dispersibility and dispersion stability is not satisfactory. Therefore, even when using a silicone resin having an extremely strong hydrophobic property, dispersibility and dispersion stability in the system of cosmetics is not satisfactory and furthermore impairs the effects of the silicone resin such as slip (lubricant property), extension (spreadability) on skin, and dry touch.
In makeup products containing powders, a cake type foundation for example, a humectant has been used to impart a moist feel for a smooth feeling, especially a smooth feeling after use on the skin. However, when cosmetics containing a humectant are applied on the skin, since the oil absorption or water absorption of the powder is too strong, the powder adsorbs the sebum or moisture, more than as required from the skin. That is, cosmetics containing a humectant lack a smooth feeling, especially a moist touch (feel), and the use of a humectant in cosmetics causes an increase in a rough feeling or a dry feeling of the skin. Accordingly, when such cosmetics are applied on the skin, it provides a hard feeling to skin, and not a soft feeling. In addition, affixture of a powder contained in cosmetics to the skin is worsened, and adhesion of a cosmetic film on the skin is deficient. Consequently, these defects also causes the makeup to come off. Especially, the rough feeling of the skin has been clearly problematic during the winter.
In order to solve this problem, the addition of a humectant such as glycerin, propylene glycol or 1,3-butylene glycol to cosmetics has been attempted so far. When cosmetics containing a powder are produced by simply mixing a humectant with other ingredients, various ingredients are used as starting materials for cosmetics to be adhered to or adsorbed on the surface of the powder, and further the surface properties of the powder become heterogeneous, and the affixture to the skin decreases. Consequently, the rough feeling and the dry feeling of the skin cannot be improved, and the makeup is liable to come off due to secretion from the skin, movement of muscles of facial expression, and the like. In addition, when the humectant is incorporated (mixed) along with the powder, the low-molecular part of the humectant is adsorbed on the powder, but the majority of the humectant is easily desorbed from the surface of the powder, so that a mere wetting phenomenon is shown. Thus, the humectant does not basically change the surface properties of the powder. Accordingly, it is impossible to decrease the rough feeling on the skin caused by the powder and improve the affixture to the skin, so that the moist touch cannot be improved and maintained. Moreover, the unevenness of the cosmetic film caused by the powder formed on the skin cannot basically be eliminated, thereby contributing to the makeup coming off the skin.
There is also a method in which affinity for water in a powder is increased by treating the powder with silica and alumina. However this method has been problematic in that the surface activity of the powder does not have sufficient dispersibility in water. Furthermore, in cosmetics containing the treated powder (silica/alumina-treated powder), the powder itself and the surface-treating agent applied to its surface become separated or dissociated. Consequently, the powder aggregates in the system, or thereby a difference between the appearance color and application color is caused. In addition, depending on the different form of cosmetics, for example, in case of a cosmetic of bi-layer type, the powder might cause a caking phenomenon to notably decrease re-dispersibility and greatly impair usability.
Accordingly, in a system in which the cosmetics (especially cosmetics of aqueous type) contain a hydrophilicaly treated powder (surface-treated powder) prepared by hydrophilicaly treating a silicone resin (particles) by the above conventional hydrophilicaly treating method of hydrophilic treatment, the particles of the silicone resin aggregate, or the dispersion stability with lapse of time is impaired. Thus, the effects thereof are hard to exhibit satisfactorily. Therefore, it is desirable to develop a powder for cosmetics obtained by hydrophilicaly treating the silicone resin (particles). Additionally, no description has been found with respect to a surface-treated powder which is prepared by hydrophilicaly treating the silicone resin (particles) which is excellent in dispersibility and dispersion stability, a dispersion and cosmetics containing the same, and the like.